Safety-means for aircraft



April 21, 1931.

R. A. M LEAN SAFETY MEANS FOR AIRCRAFT Filed Sept. 20. 1929' INVENTOE: REUBEN A. MocLEAN ATTORN EY6.

Patented Apr. 21, 1931 UNITED STATES PATENT OFFICE REUBEN ALBERT MAGLEAN, OF OTTAWA, ONTARIO, CANADA SAFETY-MEANS FOR AIRCRAFT Application filed September 20, 1929. Serial No. 394,037. a

to the air in order to remain in flight. If

the pilot inadvertently permits the speed to fall below this minimum safe flying speed the machine is in danger of falling. It is customary to equip aeroplanes with instruments which give a visual indication of the air speed of the machine, but as it is not pos sible for pilots to observe these instruments constantly, accidents sometimes occur through excessive reduction of speed.

It has also been proposed to provide audible signals operable by air pressure to close an electric circuit and give a warning signal when the speed becomes reduced beyond a predetermined safe limit. By means of such a device the pilot is automatically given a warning which cannot be ignored or overlooked.

The object of the invention is to provide an improved and simplified signal device of the type which provides an audible signal.

The invention consists in the construction, combination and arrangement of parts hereinafter described and more particularly pointed out in the appended claims. 7

Referring now to the accompanying drawings which illustrate, by way of example, various embodiments of the invention.

Figure 1 is a sectional plan of one form of the invention, showing the parts in normal position, on line 11 of Figure 2.

Figure 2 is a plan view, partially in section, on line 22 of Figure 3 showing the parts in another position.

Figure 3 is a section on line 3-3 of Figure 1.

The example illustrated in the drawings comprises a stationary casing 42 which is attached to any convenient part of the aeroplane. Slidably mounted in the casing is a hollow plunger 43, closed at its inner end and preferably flared at its outer end The plunger is pressed outwardly by a spring 44, but its outward movement is limited by nuts 45 on a stem 46. The casing 42 is provided with one or more slots 47 against which reeds 48 48 and 48 are respectively mounted. The reeds are of unequal lengthsand are each adapted to produce a distinctive note indicative of a certain predetermined speed of travel. The reeds are enclosed in a lateral tube 49. p The plunger 43 is formed with a slot 50. As the speed of the aeroplane in-. creases the air pressure acting on the plunger 43 forces the latter into the casing against the action of the spring 44, and the aperture 50 will successively register with .the apertures 47 causing the reeds to vibrate and produce notes. 'When a safe flying speed has been at-' tained the hole 50 has moved inwardly beyond the aperture of the reed 48 and the device remains silent. If the speed falls to the minimum safe flying speed the aperture 50 will move forward into register with the aperture of reed 48". If the speed continues to fall the aperture 50 will move successively over the reeds 48 and 48*, producing a more shrill note as each successive reed is passed (see dotted lines which indicate hole 50 in register with aperture of reed 48 The sound propagated in the tube 49 is conveyed to the pilots car through any convenient cond uit or other device not shown.

The invention provides an effective warning signal which is not dependent on an electric circuit, contacts or other devices which might be liable to get out of order or require frequent inspection.

The foregoing description and accomrmnying drawings are given by way of example only, and many modifications may be made without departing from the invention as defined in the appended claims.

What I claim is 1. Apparatus for attachment to heavierthan-air flying machines comprising means operated by a current of air for creating an audible signal, a member movable by air pressure and normally rendering said signal creating means ineffective and means for urging said member yieldingly towards its forward position, said member causing actuation of said audible signal creating means when said member is forced rearwardly a predetermined distance by a pressure of air depending on the air speed of the flying machine.

2. Apparatus for attachment to a heavierthan-air flying machine comprising a series of devices for producing audible signals and movable means, subject to the pressure of air caused by the travel of the flying machine, for directing a current of air against said signal devices in succession at certain predetermined speeds of travel, said devices having different characteristics so as to be capable of producing notes of different pitch.

8. Apparatus for attachment to a heavierthan-air flying machine, comprising a casing, a series of devices for producing audible signals in said casing, a plunger slidably mounted in said casing and having an aperture normally out of registry with said devices, a spring for urging said plunger yieldingly towards its normal position, and adjustable means for limiting the movement of the plunger by the spring.

In testimony whereof I affix my signature.

REUBEN ALBERT MAoLEAN. 

